Proline-rich proteins contribute about 70% of the proteins in human parotid saliva. Observations in this laboratory, coupled with those from other laboratories, suggest a stong negative correlation between basic proline-rich proteins in the parotid saliva of rats and caries susceptibility. Very little is known about factors which influence the synthesis of these unique salivary proteins. The long-term objectives of this project have been to study factors which contribute to their regulation. Observations to date in this laboratory, coupled with the findings in other laboratories, suggest that alterations in b-adrenergic receptors lead to parallel changes in the proportion of proline-rich proteins in rat parotid saliva. Thus, the present proposal was designed to study this apparent relationship. The two specific aims are (I) to test the hypothesis that changes in the proportion of proline-rich proteins in rat parotid saliva are associated with parallel disproportionate changes in b-receptor density or biologic activity and (II) to determine at what stage of postnatal development of the rat parotid gland proline-rich proteins appear. A delay in their appearance until b-receptors exhibit biologic activity would support the hypothesis. In these studies the proportion of proline-rich proteins in parotid saliva will be correlated with b-receptor density or biologic activity. The composition of proteins will be determined by densitometric scanning of color positives taken of acrylamide gels following SDS-PAGE. These findings will be correlated with studies which test the biologic activity of the b-receptors as well as their density. The former involves in vitro assays of the ability of receptors to respond to an appropriate stimulus; the latter involves radioligand binding studies for quantitation of numbers of receptors. The proposed work may result in a better understanding of factors which regulate this unique group of salivary proteins.